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EDWIN S. GOODRICH. 



diura, which may or may not represent single somites." The 

 first somite with parapodia, chsetse, and acicula he calls the 

 ''peristomiura." 



Fig. 1. 



Tig. 2. 



Fig, 1.— -Ventral view of a young Nereis. 



Fig. 2. — Diagrammatic plan of the anterior segments of the Polycbseta. The 



nervous system is represented in black, the mesoblastic tissues are 



dotted, the coelomic cavities are left white. F. P. Frontal process. 



m. Mouth. Pa. Parapodium. Pr. Prostomium. T. Tentacle. A. 



Archicerebrum. The Roman numbers refer to the segments. 



The prostomium (Kopflappen, lobe cephalique), then, is a 

 median anterior process lying above and in front of the 

 mouth. It may be small and insignificant, as in most Oligo- 

 chaetes, or it may be large and of great physiological im- 

 portance, as in many Polychaetes. The prostomium may be 

 long and produced into a moveable process (Stylaria), or 

 distinctly annulated (Glycera). In the Polychseta it contains 

 the brain or supra- oesophageal ganglion, and often bears 

 specialised organs of sense, such as dorsal tentacles and eyes, 

 and ventral palps. In the Oligochaeta, on the other hand, the 

 brain recedes from the prostomium (except iEolosoma) into 



